The present invention refers to self-propelled crane vehicles of the type referred to in the generic clause of claim 1 and comprises in particular a new frame and support structure which is especially suitable for crane vehicles.
Self-propelled crane vehicles must fulfill a large number of demands in order to be admitted to the traffic on public trunk roads. In Germany the provisions of the StVZO (Road Traffic Licensing Regulations) apply in this respect.
These demands comprise a minimum cruising speed on public roads of 62 km/h and a visual range diameter with a radius Rxe2x89xa612 m for the driver. To be allowed to travel without being accompanied by the traffic police, the maximum width of the crane vehicle should be less than 3 m. In view of the limited headroom under road bridges, the overall height of the crane vehicle should be xe2x89xa64.0 m when the crane vehicle is travelling. Certain limitations exist also with regard to the own weight in view of the limited load-bearing capacity of bridges.
Crane vehicles have a chassis with a stable frame extending in the longitudinal direction of the vehicle and in the middle of the vehicle. In the case of most of the conventional structural designs, the axles of at least two pairs of wheels extend below this frame, part of said pairs of wheels being drivable and steerable. The wheels are secured to the frame with the aid of suitable wheel suspensions.
The frame has also connected thereto the support means which are indispensable for operating the crane and on which the crane vehicle rests when the crane is in operation. In the case of a normal four-point support, four extendable and/or pivotable support beams are provided, each of the free ends of said support beams having attached thereto a hydraulic support cylinder and a supporting plate. The conventional support beams are extended and/or pivoted transversely to the longitudinal axis of the frame to such an extent that there will be sufficient safety against overturning when the crane vehicle is hoisting loads. Normally two support beams which are adapted to be extended in opposite directions are provided in the area of the front end of the vehicle frame and two support beams which are adapted to be extended in opposite directions are provided in the area of the rear end of the vehicle frame.
Above the frame a ball-bearing slewing ring is provided, which rests on said frame and on which the crane superstructure 300 in its entirety is supported. The crane superstructure 300 comprises a frame which is referred to as turntable and which has supported thereon the crane mast (jib) with its articulation member and its telescopic components as well as the luffing gear required for raising the crane mast. It goes without saying that every self-propelled crane vehicle is equipped with suitable driving and steering means for the chassis, drive means for the turntable and means for operating the luffing gear and for extending and retracting the telescopic components as well as for hoisting and lowering loads.
FIG. 6 shows a four-point support which is suitable especially for crane vehicles designed for loads up to approx. 400 t. The figure shows the vehicle frame 111 which extends in the longitudinal direction of the vehicle and which is provided with a front support means 114 at the front end thereof and with a rear support means 115 at the rear end thereof. The support means 114 and 115 are secured to hydraulically extendable support beams 111xe2x80x2 and 111xe2x80x3. Each of these support beams can be extended by approx. 1 m in the longitudinal direction of the frame.
In the area where the slewing ring 124 is supported, a left support beam 130 and a right support beam 132 are supported. These two support beams are adapted to be extended from respective reception cases 134 and 136 in opposite directions to the operating positions shown, and they are provided with support means 116 and 117, respectively, at the free ends thereof. The eight wheels of a four-axle crane vehicle are designated by reference numeral 107 in FIG. 6.
When the crane is in operation, each crane vehicle rests on the support cylinders alone, whereas the vehicle wheels are no longer in contact with the ground, the support cylinders absorbing the respective reaction forces.
The known crane-vehicle support according to FIG. 6 offers construction-dependent great advantages, but it is comparatively complicated and expensive as far as production and maintenance is concerned.
Hence, it is the object of the present invention to provide a crane vehicle or rather a four-point support for crane vehicles whose structural design permits in comparison with conventional structural designs simpler production and maintenance.
This object is achieved by the subject matter of claim 1 and the subject matter of claim 6, respectively.
Due to the fact that the undercarriage construction can be very low in the case of the crane vehicle according to the present invention, larger dimensions of the crane mast (jib) can be chosen, which will increase the hoisting capacity without any increase in the overall height of the crane vehicle. To the person skilled in the art it is known that in the case of a crane mast an increase in the flexural strength, i.e. an increase in the load-bearing capacity, can be achieved by increasing the height. The reduction of the own weight that can be accomplished in the area of the undercarriage of the crane vehicle according to the present invention permits an increase of the own weight in the area of the crane superstructure 300, in particular in the area of the crane mast, without increasing the overall weight of the crane vehicle. The reduction of the own weight that can be accomplished by the present invention in the area of the undercarriage can, for example, be utilized for increasing the number of telescopic jib components which can be accommodated in a crane jib of predetermined overall height.
It should here be emphasized that the four-point support having the structural design according to the present invention is suitable not only for crane vehicles of the type described and disclosed in the present application but also for crane vehicles whose jib head has a completely different structural design. The crane jib can e.g. have associated therewith an extandable fire ladder or the jib can be implemented as an extendable fire ladder. In addition, units, such as working platforms etc., can be provided on the free end of the jib.
A characteristic feature of the four-point support according to the present invention is that the support member(s) are not accommodated in special support cases but are accommodated directly in the longitudinal vehicle frame. In the case of extendable (telescopic) support members, it proved to be particularly advantageous when an outer support member in the form of a hollow body is arranged in the longitudinal vehicle frame, either in a stationary or in a displaceable mode of arrangement, and when an inner support member is displaceably supported in said outer support member. The outer free end of this inner support member has provided thereon a support cylinder with a supporting plate.
The support means according to the present invention, in the case of which conventional support cases can be dispensed with, results in a substantial reduction of weight, since the introduction of forces can be optimized with regard to lateral forces and bending. Furthermore, the whole connection of the support members to the longitudinal vehicle frame can be established in a comparatively simple manner.
Preferred embodiments of the present invention are disclosed in the subclaims.